It has heretofore been proposed to package finely ground coffee in a bag or packet of a pervious filter material, similar to a tea bag, which can be placed in a cup or other container of hot water to be left to "brew" for a certain length of time and then removed for consumption of the coffee. There are problems with coffee in that, unlike tea, it rapidly deteriorates in the presence of the oxygen which is present in the atmosphere. In the Hiscock U.S. Pat. No. 3,330,668, issued July 11, 1967, a method is disclosed in which such packets are disposed in a sealed outer wrap of an impervious material, containing an inert gas such as carbon dioxide to surround the packet within the sealed outer wrap and to prevent exposure to oxygen and deterioration of the coffee. On an experimental basis excellent results can be obtained and, prior to this invention, a machine was constructed for the packaging of coffee and intended for using carbon dioxde in accordance with the teachings of the Hiscock patent.
In the machine so constructed, a web of a pervious filter material is folded along a longitudinal fold line to form a generally V-shaped trough, the web being supported by an endless conveyor structure having upwardly projecting fingers which receive the web at spaced points therealong. The web is then severed to form individual packets. The web then moves through a filling region in which predetermined quantities of ground coffee are supplied, thence to a sealing region in which portions of the web are adhered together ahead of, above and behind each discrete quantity of the ground coffee. Such packets are supported from above by fingers depending from another endless conveyor structure to be carried to move along and above a web of an impervious outer wrap material, also folded to form a generally V-shaped trough. The packets are gently lowered into the web of wrapping material to be disposed in longitudinally spaced relation therealong, the web of wrapping material being moved longitudinally toward a sealing region in which portions thereof are sealed together ahead of, above and behind each packet and the discrete quantity of coffee contained therein. The web of wrapping material is then severed to form individual packages which may be carried by further apparatus to be placed in suitable boxes.
It is impractical to try to operate such apparatus in an enclosed space filled with gas to be substantially free of oxygen, for various reasons including the fact that it is not possible to avoid occassional problems and jam-ups in the operation of the machine in the forming and handling of the relatively delicate and lightweight packets of coffee, especially when the machine is operated at high production rates of speed. Frequent access to the machine is a practical necessity. To avoid operating the entire machine in an oxygen-free environment, attempts were made to "flood" the folded overwrap material with carbon dioxide, without substantial success, even with a very high rate of flow, at which freezing became a problem. Attempts to provide a cover in the sealing or crimping region did not produce satisfactory results and also resulted in problems because of the heat developed by the sealing or crimping apparatus.